Climate Science Glossary

Term Lookup

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Term:

Settings

Beginner Intermediate Advanced No DefinitionsDefinition Life:

All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 30 December 2011 by Andy Skuce

Here is a translation of recent article (December 25th, 2011) in the French newspaper Le Monde by science journalist Stéphane Foucart. He reports on a talk that Michael Mann gave at the 2011 AGU Fall Meeting in San Francisco, in which Mann introduces his forthcoming book The Hockey Stick and the Climate Wars: Dispatches from the Front Lines. Foucart interviews Mann and discusses the background of the Hockey Stick and Climategate controversies. What is refreshing is the absence of the false balance, both-sides-of-the-story, style of reporting that is found so often in English language newspapers.

In early December, at the Fall Meeting of the American Geophysical Union (the annual grand gathering of the bigwigs of the geoscience world), Michael Mann introduced his forthcoming book to his peers. The lecture was entertaining and the audience laughed heartily. The American climatologist, Director of the Earth System Center at Pennsylvania State University, cracked numerous jokes and made many witty asides. He scoffed at the anti-science of the Republican politicians and mocked their ridiculous statements on climate change; everybody laughed out loud.

But this, surely, is no laughing matter. Michael Mann’s forthcoming book, The Hockey Stick and the Climate Wars: Dispatches from the Front Lines (Columbia University Press), is not really a science book; rather, as its title suggests, it deals instead with the war on climate science, which has at times turned into a manhunt, frequently with Mann as the quarry.

Lively, talkative and likeable, passionate about his research, Michael Mann is Conservative America’s most hated scientist. His crime is defined by two words, Hockey Stick, the nickname given to a curve showing how temperature has changed; a diagram that he will now forever be associated with.

In 1998, and again in 1999, with co-authors Raymond Bradley and Malcolm Hughes, he published a “reconstruction” of Northern Hemisphere temperatures, from the year 1000 to the present day. Using the traces of past climates recorded in tree rings, corals and sediments, he succeeded in producing a striking curve in the shape of a hockey stick. The long handle shows a fairly regular decline in temperatures from 1000 to around 1900, whereas the blade displays a sudden and a rather worrying sharp upward increase that is very obvious since 1950. The main conclusion of the Hockey Stick is that the last decade of the twentieth century was probably the warmest in over a thousand years.

“The irony is that I wasn’t originally working on anthropogenic climate change but on natural climate oscillations”, says Michael Mann. “I wasn’t looking for a hockey stick; it simply emerged from the data!”

The curve was given pride of place in 2001, in the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). It provided a striking visual image of the climate emergency. It became a symbol, and consequently, for all climate skeptics, an icon to destroy.

There began, at the beginning of the past decade, “an intense campaign of defamation, essentially financed by industry”, according to Mann. A statistician—also a consultant for the fossil fuel industry—disputed the data processing that produced the famous curve. The basic data themselves were subsequently put under suspicion and soon Mann was accused of having deliberately manipulated them. The Internet became awash with all kinds of myths linked to the Hockey Stick, urban legends that are occasionally passed on by scientists misled by the technicality of the arguments put forward. It is impossible today to Google the term Hockey Stick without finding hundreds of pages that detail alleged frauds, intentional errors and manipulations attributed to its creator.

The campaign worked wonderfully. In 2006, an American Congressman asked mathematician Edward Wegman (George Mason University) to prepare a report on the famous curve. The “Wegman Report” piled on with more criticism of the Hockey Stick. The American National Academy of Sciences was soon put to work to produce a report on the Hockey Stick, but they didn’t find much to complain about. “There was a legitimate technical discussion on the statistical method used in the data processing”, said Pascal Yiou (with France’s Climate Science and Environment Laboratory), “but others have processed the same data with different methods and that didn’t change the shape of the curve”.

Above all, as the controversy was artificially kept alive on the Net, a dozen other temperature reconstructions reached the same general conclusions as the original Hockey Stick.

The attacks were not just restricted to the iconic curve, however. Its author also was personally targeted. At the end of 2009, his emails—along with those of a number of other climatologists— were pirated and published on the Web. Most of the sentences, taken out of context, suggested collusion. A Republican Senator called for an enquiry into several researchers, Michael Mann first among them. The Attorney General for Virginia demanded that Mann’s Alma Mater, the University of Virginia, hand over all documents relating to him, including his archived emails, to search for possible evidence of fraud. As for Pennsylvania State University, it was pressured in 2010 to open an investigation on Mann, but ended up exonerating him.

Michael Mann feels that things can get carried away at times. “One day, a year and a half ago, I received a letter with white powder inside it that looked like it could be anthrax. I forwarded the letter to the police who sent it for analysis: it turned out to be corn flour.” Since then, he won’t open letters unless he knows the sender.

How does anyone survive almost a decade of attacks and slander? “Getting caught in such storms isn’t something that scientific training prepares you for”, he says. “You have to become expert in defending yourself and dealing with misinformation and attacks. But I like a fight!” When the attacks started to focus on him, one of his mentors, the late Steve Schneider (Stanford University), suggested to him that if “they” were coming after him, it was because his work was important. “That was really something that helped me to have the courage to face all this”, he says.

What, ultimately, is the outcome of all this? He suddenly becomes less talkative. “Those who attack us have won in the sense that they have succeeded in delaying any action on global warming by ten, twenty, maybe thirty years,” he concedes with worry as he sees his country succumbing to anti-science. “Denying either anthropogenic climate change or evolution has become a condition of admission to the Republican Party. That’s something quite new and very scary”.

By Stéphane Foucart

(Translated by Andy S. Please note that the quotes attributed to Mann were translated back into English from the French version of his words as reported in Le Monde. They will not therefore correspond exactly to what he originally said.)

Further reading: additional translations of newspaper articles and commentary (in English) on the reporting of climate change controversies in the French press can be found here.

Comments

A quick advance heads-up for those who live in Southern California (or will be in SoCal in February). Dr. Mann will be speaking at the Aquarium of the Pacific in Long Beach (near Los Angeles) on Feb 15.

I wouldn't be surprised if this event brings some noisy detractors out of the woodwork, so anyone who happens to be in this neck of the woods (or what passes for woods in SoCal) on Feb 15 should consider dropping by and giving Dr. Mann a show of support.

Rohrabacher, btw, is now serving in his 12th term, and IIRC has never had to sweat re-election. Keep that in mind as you watch the video.

There are lots of hard-core Rohrabacher supporters living pretty close to where Mann will be speaking, so heckling wouldn't be unexpected. In fact, given the political views of many in that area (especially to the south, in Orange County), there's the possibility of being treated to a bit of a right-wing "freak-show" outside the venue.

Folks attending might want to have their videocam/iphone/android devices handy. There's the potential of getting some very "YouTube worthy" video footage.

What, ultimately, is the outcome of all this? He suddenly becomes less talkative. "Those who attack us have won in the sense that they have succeeded in delaying any action on global warming by ten, twenty, maybe thirty years," he concedes with worry as he sees his country succumbing to anti-science. "Denying either anthropogenic climate change or evolution has become a condition of admission to the Republican Party. That’s something quite new and very scary".

And therein lies the rub.

The Denialati have already won. It matters not to the eventual inevitable public vindication of the science, because the vested interests and the ideologues have achieved the delay they sought. And those ten to thirty years represent the difference between a relatively livable world to bequest to future generations, and one where the global indices of human suffering and of ecological integrity are seriously compromised.

It only remains to be seen by how much humanity intends to allow those indices to be seriously compromised.

That such politically-driven obfuscation of scientific fact can occur in both the USA and in Australia (amongst other countries) indicates a fundamental failing in both our societies. I suspect that as well as future generations cursing our current national propensities for overweening social self-indulgence, future historians will be less than complimentary about the decision-making processes of which we are apparently so proud.

It seems that in its capacity to achieve sensible conclusions, science has much to teach political democracy. This is reflected in the incredulity so many scientists experience when lay people accept the misrepresentation of solid work such as Mann's. It is telling that the situation appears to be different in France.

I suspect at least some amongst those aforementioned future generations would be less horrified, on reflection and with their benefit of hindsight, if Micro$oft Vista (another famously buggy operating system) had been introduced to the world in 2000 at the end of a gun...

If only it wasn't oxymoronic to introduce rational thinking to the US and Australia in the same way.

Steve McIntyre was a hired gun out of the Fraser Institute; he packed a statistical toolkit to unravel formulas that produced an inevitable hockey blade - from any data. As the Rounds piled up, his attack shifted to the data (notably the Briffa backfire). His current universe has degraded into e-mail gossip smears. The biggest problem with an audit of his critique is the utter failure to produce a reconstruction that could anchor his attacks.

The irony is that he abandoned his main attack - on the formula - and by implication gave it a measure of approval. Indeed, if the flaw was in the formula there was no need for a decade of data attacks (his latest claim versus the hockey team is that they all use the same flawed data).

Mann's reconstruction has been wiggled and jiggled by subsequent independent lines of research ... but the observations and data match his thesis. And mock McIntyre.

There is a problem with dodgy thinking in democracies. People are susceptible to superficially attractive arguments. This doesn't matter if politicians and the media choose not to use factually wrong but attractive arguments. But if they do, we have a real problem.

Take taxation. During the decade long boom leading up to the GFC, governments should have taxed more. Its easy to see in hindsight, now that governments around the world find themselves with unsustainable levels of debt. But it should have been foreseeable, and politicians on both sides should have spurned tax cuts, arguing instead for caution. But if you want to win an election, you should promise tax cuts, and the media should cheer you on.

Its the same with global warming - its easy to be irresponsible and encourage people to deny that we have a problem. The Republicans in the US, and the Coalition in Australia have decided to play the populist card. The Murdoch media has gone along with this. It is annoying, to say the least.

@5: Great Alley - Rohrbacher video. Thanks for posting. For those who don't have time for the whole 10-minute video, go to 5:46. Alley to Rohrbacher: "If you sort of go to the far fringe, it just might be about where you are..." Brilliant!

Steve McIntyre was a hired gun out of the Fraser Institute; he packed a statistical toolkit to unravel formulas that produced an inevitable hockey blade - from any data.

(Disclaimer: The material below is a non-rigorous, "arm-wavy" attempt to explain in plain English to non-mathematical types, why the "Mann generates hockey sticks from any data" argument is bogus -- it is by no means a "proper and correct" explanation from a rigorous mathematical perspective.)

I should weigh in here, since I have some relevant experience with the SVD (Singular Value Decomposition) algorithm (the algorithm Mann used to "merge down" his North American tree-ring data). Although it is possible for Mann's SVD implementation to produce a "hockey-stick-shaped" leading principal component from random noise, no competent analyst would ever confuse such a "noise" hockey-stick with the genuine article.

When an SVD run produces a "hockey stick" leading principal component, the full SVD output will tell you two things about that "hockey-stick" leading principal component: its shape, and even more importantly, its *size*. Mann's method applied to tree-ring data produces a *big* hockey stick; if you get a hockey stick when you apply Mann's SVD to random noise, that hockey-stick will be tiny -- much smaller than the genuine Mann tree-ring hockey-stick.

To determine the hockey-stick "size" (aka magnitude), you need to look at the magnitude of the leading singular value. Each principal component aka singular vector has an associated singular value. The size of the singular value will tell you whether the associated principal component represents a "lot" of the data or just a "little" of the data.

If you look at the leading singular values for a bunch of "noise hockey-stick" runs, you will see that those leading singular values are *much* smaller than the singular value associated with Mann's tree-ring leading principal component.

If your SVD produces a small leading singular value, with the other singular values trailing off gradually in magnitude, then you will know that your data vectors are mostly uncorrelated with each other (i.e. they will have little or no "common temperature" signal). That's the signature of random noise.

OTOH, if your SVD produces a large leading singular value, with the remaining singular values decaying very quickly to near-zero magnitudes, you will know that your data vectors are highly correlated with each other, and most likely share strong common temperature signal. Can you guess what Mann's singular values looked like?

You can see a plot of the first ten (out of 70) of Mann's singular values here:

The blue circles represent the singular values (actually eigenvalues which are singular-values squared, but that doesn't matter here) generated by Mann's "short-centered" SVD procedure (the procedure skeptics claim produces hockey-sticks from noise). As you can see, the singular values decay (roll off) rapidly to near zero. Nearly all of the information in the tree-ring data set (70 tree-ring time-series) is captured by just the first three or so singular values. That's a good indication that the 70 tree-ring time-series in Mann's data set are highly correlated and thus share a strong common temperature signal.

Note: The singular values not plotted (singular values 11-70) are all *very* close to zero. If the above plot had shown all 70 singular values instead of the first 10, the "sharp roll-off" nature of Mann's tree-ring singular value spectrum would be even more obvious.

Some time ago, I experimented a bit with SciLab (scilab.org) and was able to generate my own "noise hockey sticks". But when I looked at my singular values, I found that those "noise hockey-stick" singular values looked *nothing* like Mann's tree-ring hockey-stick singular values. The leading singular value (associated with the "hockey-stick" leading principal component) generated from random noise was always very small (a small fraction of Mann's leading singular value), no matter how "hockey-stick-shaped" the leading principal component was. The remaining singular-values trailed off very slowly in size (producing a clear "random noise" singular-value signature).

The bottom line is, unless you look at the singular values, you can't say *anything* about your data. You can't simply look at the principal components (aka singular vectors) without considering the associated singular value magnitudes and draw any reasonable conclusions about whether your data vectors contain a "common signal" or are just random noise. Without the information provided by the singular values, you simply can't tell (no matter what your principal-components look like).

But that's exactly what skeptics did when they attacked Mann by claiming that his procedure generates hockey sticks from random noise. They never bothered to compare their "noise hockey stick" singular values with Mann's "tree-ring" singular values. Those of you out there who are familiar with the SVD and know how to interpret its output will fully appreciate what a spectacular blunder this is. Unfortunately, for most people, the SVD is obscure enough to them that they will never appreciate how stunningly incompetent the "Mann method generates hockey sticks from random noise" argument really is.

What bothers me most about this is how the attacks on Mann were amplified in mainstream media. Here’s an example from Canada; On December 12, 2009, Licia Corbella, a senior editor of the Calgary Herald, published a column entitled ‘Real scientists should care more about fraud’. In her column, she stated that Michael Mann “…is already a discredited scientist, as his hockey stick graph was proved to be false years ago.” This was particularly hard to swallow given the profound ignorance Corbella had previously demonstrated regarding climate science. In a column entitled ‘Check the record and it's hard to take Suzuki seriously’ published in February 2008 in the Calgary Herald and the Vancouver Sun, she stated “…according to ice core data, when CO2 levels were 16 times higher than they are today, Earth was covered in ice.”

The bottom line is that Corbella’s slanderous statements and remarkable version of the ice core records were widely read in what are usually considered to be respectable newspapers. Both the Calgary Herald and the Vancouver Sun refused to publish any ‘letters to the editor’ that countered Corbella’s attack on Mann and I know that my letters were not the only responses that were submitted.

Especially incompetent in the face of all the other hockey sticks that are not from SVDs: atmospheric CO2, Arctic ice (blade is down), sea level (see the SkS graphics page for North Carolina), etc. It's one thing to incompetently say 'the hockey stick is generated from noise' -- its quite another to have to stick with that position over and over again.

But thanks for that lucid explanation of the Singular Value Decomposition (SVD). I've described it to my Linear Algebra classes as 'the best thing since sliced bread.' Should anyone want to try to see what they obtain from random noise, try this applet on an appropriately randomly seeded matrix.

I could not agree more. Bernard J’s “Denialati”, are winning the war whilst losing every battle. This side of the fence has to decide whether their welfare and that of their descendants is going to be best served by continuing to play 'Mr Nice Guy' and sticking rigidly to the science, or if the time has arrived for more direct action. Though the last thing I am suggesting is that sks should sink to the level one finds elsewhere on the climate issue. Perhaps a ‘direct action’ thread could suffice as a nucleus around which some form of organisation for direct action could grow.

The Occupy Wall St. Movement has gained a lot of publicity and not a small amount of public support for their unclear cause(s), yet Climate Change is about the possible deaths of countless numbers of our descendants, if not those of us still alive, and is surely a more deserving and clearer cause.

I have suggested before that there is soon to be an excellent opportunity to show the ‘retarded right’ how we feel about their contempt for the rest of us and our descendants. I make no apology for the repetition. The opening ceremony of the London Olympics next year will be performed mainly by the younger generation, who will be the ones most likely to suffer the privations that climate change will heap upon the planet. If those taking part could be encouraged to carry a placard demanding action on the topic, then at least we can be sure that they will be seen by countless millions. Any national committee that bans the action could be named and shamed. Perhaps even more dramatic action could be considered, such as a refusal to take part in the opening, which the national committees would be hard pressed to ban.

I honestly don’t think that the debate can keep plodding on while The Denialati keep managing to postpone action that is now so urgently needed (re the sudden release of methane in the Arctic as noted recently by Russian scientists, which, if it proves to be the long feared methane ‘burp’, then I guess it’s game over). The debate has now been going on for so long that all with an open mind will have made their mind up on the issue. By all means continue with the excellent scientific analysis, it is still important, if only to provide evidence in any future criminal proceedings regarding the actions of The Denialati. But the debate has to go up a gear if meaningful change is to happen and our descendants are not to be destined to a bleak and overheated future.

@12 -- thanks. I'm not too scared of stats but I have never wanted to waste much time on trying to see what all the fuss was about wrt the hockey stick. The closest I got was reading the discovery of Wegman's sloppy copy-catting of McIntyre's cherry-picking. Some day, someone will produce a good basic, intermediate, and advanced page regarding the entire hockey stick story at SkS ... and I'll read it! (The link to the Alex Lockwood overview from the most relevant SkS page is broken -- that SkS page is pretty good, but I'm not sure that it's comprehensive of the false skeptics' complaints including withholding data, upside down proxies[?], and whatever else they yammer on about.)

@5, I watched the video and was annoyed. Dana Rohrabacher wanted to attack Alley with specific questions and wanted to limit Alley's ablity to answer ("15 seconds"); then he gets confused and he turns to Michaels with just an open mic. These guys are pretty frustrating -- they want to apply parsimony when it comes to Mars (and ignore natural variability due to cyclicity and dust), but for the Earth they'll imagine undetectable cycles in the sun causing unspecified cloud changes that nobody has noticed.

On the constructive (but unfortunately off-topic) side, I decided to learn a bit about Mars. I was hoping to find a sort of cryosphere today for martian polar ice cap area or extent, and then look at trends over time to see how well they match up with Earth's. Or to see at some point in the future when the trends diverge. No luck. Also there's a huge fluctuation in the CO2 content of the martian atmosphere (a bunch of the ice is frozen CO2) such that atmospheric pressure fluctuates by 25% over the year. I haven't yet found much written on the climatological impact of greenhouse gases there. But I think that would be interesting.

caerbannog @12, would you please write that comment up as an article that can be posted on SkS. Ideally you should have two versions. A basic version which would essentially reproduce your comment, and an advanced version which includes discussion of the maths, and references to basic textbooks so that people not familiar with the maths can check the veracity of what you say themselves.

is a clear example. You can follow the trail from the think tanks E/M funds/has funded to blog sites like Junkscience.com (via the Cato Institute). Steve Milloy at that blog site and in his column in The Weekly Standardhas smeared plenty of climate scientists, including Michael Mann.

...Just checked in there, and there is a picture of a hockey stick right at the top with some a bumper sticker blurb on the parlous state of intellectual integrity in climate science. A quick search finds such gems as

http://junkscience.com/2011/12/06/steven-hayward-responds-to-mann/

....I refer to Michael “hockey stick” Mann as the Fredo of the climate mafia, because of his endless bluster and the obvious embarrassment he brings to his fellow scientists.... At this point it is difficult to tell if Mann is simply delusional, or a deliberate liar.

But it's very easy to find links/details/evidence to this and many other examples with some ordinary search terms on google. So I wonder dawsonjg if your question was argumentative rather than genuine?

Mann's "short centering" (as opposed to full centering) prior to the SVD calculation was indeed a mistake -- but an inconsequential one.

The singular-value thresholding procedure (i.e. the algorithm that Mann used to decide which principal components to retain) ensures that the final results will be the same no matter which centering convention is used. See Mann et al. (or realclimate.org) for details.

Apply Mann's thresholding procedure to "short-centered" SVD outputs and it will give you the proper answer as to how many principal components to retain. Apply the same thresholding procedure to "full-centered" SVD outputs, and it will still give you the proper answer as to how many principal components to retain.

The bottom line is, no matter which centering convention you use, there is a *huge* (as in night vs. day) difference in the singular-value patterns for tree-ring data vs. random-noise data. Anyone who claims otherwise simply does not know what he/she is talking about.

But folks don't need to take my word for it -- there's lots of free software out there that allows you to "roll your own" random-noise hockey-sticks. Do that, compare your full-centered and short-centered random-noise singular values with Mann's tree-ring eigenvalues (both full- and short-centered), and you will see that it is slam-dunk easy to tell the difference between tree-ring data and random-noise data *simply by looking at the singular values*.

An excellent software package that has everything you need to do this is SciLab (www.scilab.org). It runs on Linux, OS-X, and Windows platforms. Easy to install, easy to run, not that hard to learn how to write your own script files.

Out of a bit of sloppiness, I used "singular values" and "eigenvalues" interchangeably in my above post. As far as Mann's application of the SVD procedure is concerned, they represent basically the same thing (eigenvalues are just singular-values squared).

I do not understand why we continue to discuss the details of Mann 98 and 99 anyway. These papers have been superceded by many other papers that have corrected any supposed mistakes and shown that Mann 98 was correct. The main conclusion is Mann 98 is an example of great work that advanced the science.

caerbannog @25, given that the red crosses show the full centered SVD, as used by M&M, and given that there is significant information out to at least the fifth Principle Component as shown on your graph, would you then agree that M&M did make a consequential error by only including two principle components in their reanalysis of the MBH data?

#26
would you then agree that M&M did make a consequential error by only including two principle components in their reanalysis of the MBH data?

Absolutely.

M&M failed to apply Mann's singular-value selection algorithm properly to the full-centered data. The fact that they blindly stuck with two principal components with the full-centered approach indicates that they didn't know what they were doing. Even a quick "eyball analysis" of the "full-centered" singular values would tell you (actually *scream* at you) to include more principal components.

There are lots of people out there who may be whizzes at crunching data with mathematical tools like matlab/scilab/R/etc., but that doesn't mean that they know how to interpret the results they get.

@25, that's a fair question. For me it's largely interesting because I want to understand why AGW-deniers find it so compelling. Why are they putting so many of their eggs into this basket?
In addition, because of their focus on it, it's always topical. Whether it's Cuccinelli or AFP, the media plays as though some kind of trump card over the science could be found by someone digging through email. People who know anything about science know there is no such card. But when I talk to someone skeptical of science, and they refer vaguely to any number of supposed scandals involving Mann, I would like to know better than they do the history of the complaints they're trying to echo.
I would go look at McIntyre's website for a history, but there's a lot of chaff to separate and, besides,as @8 suggests, McIntyre's story has changed and he might not be reliable even at summarizing his own claims against Mann et al (both personal and statistical).

Thank you Barry for taking the time to adress my question, but I can't have made it clear. Mann and the above article imply that McIntyre's work that discredited the hockey stick was part of “an intense campaign of defamation, essentially financed by industry”, i.e. that McIntyre was being funded to come up with a way of defaming Mann et al. That is quite a (defaming) accusation. I just want to know what it is based on. We know who was paying Mann to do his work, can anyone tell me which industry vested interest was paying McIntyre to do his?

dawsonjg @29 McIntyre's work was part of an intensive campaign, and that campaign has been funded by industry, but Mann does not say that McIntyre himself, or his website have been funded by industry.

The fact is that McIntyre has cooperated with scientists who are both active in the campaign against climate science, and are known to have been funded by fossil fuel companies for activities undertaken in that regard. He has also attended and spoken at conferences organized by think tanks again known to be funded by fossil fuel interests. That makes him part of the industry funded campaign even though he is not paid by industry in that capacity. (He was paid by a fossil fuel company in a professional capacity up until 2003, but I know of no evidence to suggest he has been paid for his "work" at Climate Audit.)

What is more, McIntyre's claims have certainly been taken up and echoed around by industry funded individuals and organizations. That is all that is needed for Mann's specific claim to be true. His claim is, ergo, not defamatory for it is true. If you think it reflects poorly on McIntyre, well you are certainly welcome to that opinion.

There were TWO congressional investigations, one at the request of Congressman Sherwood Boehlert(R) of the Science Committee. It was chaired by Professor Gerald North of Texas A&M. The report was critical of some of the methods used by Mann and his colleagues, but in the main supported the conclusions.

However, this report seems to have been deemed insufficiently critical in some quarters. A second Congressman, Joe Barton (R) of the Energy Committee requested another report, chaired by a group under Professor Edwward Wegman of George Mason University. The subsequent history of the Wegman Report is well known - the part of it published in Computational Statistics was subsequently withdrawn for plagiarism. Opinion is that it is a thinly-disguised rehash of McIntyre and McKittrick's earlier papers, leavened with material taken from Wikipedia (among other sources).

The Wegman Report went ahead over the objections of Congressman Boehlert who wrote to Barton that the second investigation was "misguided and illegitimate". Subsequently, Boehlert retired - after the Republican victory in 2010, the Science Committee of Congress was amalmagated with the Energy Committee under Congressman Barton. Joe Barton is notorious for apologising to BP for the obloquy the company received over the Gulf Oil spill.

How Congressional staffers, the Wall Street Journal, and Wegman collaborated to disseminate MacIntyre's ideas and morph him into a "science superstar" (to whom?) can be found on several blogs. Here is a good start:

Dawsonjg,
You are incorrect when you claim "McIntyre's work that discredited the hockey stick". Mann's work has been reproduced and validated by numerous independent groups. Mann himself has updated the original graph several times. McIntyre's work is the material that has not stood the test of time (see 27 in this thread).

Tom Curtis at 11:34 AM on 31 December, 2011
caerbannog @12, would you please write that comment up as an article that can be posted on SkS. Ideally you should have two versions.

Got a bit of a full plate right now, but will get started on putting together an article when I find some free time (hopefully within the next couple of weeks or so).

00

Moderator Response: It might be better as a modification of the existing "Hockey stick is broken." A mention in the Basic version, an expansion in the Intermediate section, and the full expansion in the Advanced version. (Only the Basic version exists right now, so other authors could pitch in to add the material other than yours for the two new versions.)

So Mann became an internationally acclaimed hero for producing a hockey stick graph for the 2001 IPCC report that eliminated the Medieval Warm Period and Little Ice Age and showed an unprecedented 20th century rise in temperature; then McIntyre claimed at climate denial conferences that Mann was wrong to eliminate the MWP and LIA, which amounted to industry funded defamation. But McIntyre and the denialists who paid his travel expenses didn't know what they were talking about. Have I got it now? But hang on a minute - hasn't the MWP and LIA reappeared in subsequent IPCC reports?

00

Moderator Response: The Medieval Warm Period is discussed in the Skeptical Science argument "Medieval Warm Period was warmer." The Little Ice Age is discussed in "We’re coming out of the Little Ice Age." Please read both of those posts to learn, before you comment more. And consider that perhaps your comments are more relevant to those threads than this one.

dawsonjg - noone is disputing that the original Mann paper has flaws and has been improved but the cross-proxy method that the paper pioneered is the norm now. What modern reconstruction is there that eliminates the hockey stick?

And consider that perhaps your comments are more relevant to those threads than this one.

I think dawsonjg's comment is relevant to this thread in the sense that it is a great illustration of how some people are perfectly willing to denigrate Mann despite demonstrating that they know little or nothing about the science ...

Saying Mann got is wrong (as some of you acknowledge) is denigrating him dhogaza? Hounding him? Denigrating him? But accusing McIntyre of being part of an industry financed defamation campaign because he might be paid travelling expenses to speak at conferences that might receive donations from industry is fair cop?

"Got it wrong" is not correct. There is a hockey stick. The methodology is fundamentally correct. It was not warmer in the MWP. The assertion that you can make a hockey stick with any data is using Mann's original method is wrong. Mann's original method could indeed be improved and the science moves on as it does in so many other areas.

McIntyre however does not move on, and nor do supporters - it seems pretty obvious why not to me.

dawsonjg @39, the defamatory campaign against Michael Mann does not simply say he was wrong. They accuse him of deliberate fraud. Indeed, googling "Michael", "Mann", "fraud", "MWP" turns up 2,390,000 hits so the campaign is extensive. Further, McIntyre did not just say Mann was wrong. Searching his site for "Mann", "Fraud" turns up 32 articles. And, quite frankly, you did not just say that Mann was wrong. Your original, and demonstrably false, claim was that Mann had defamed McIntyre.

There is no point coming over all coy and innocent. The corpse is on the floor, the blood is all over you and the knife is in your hands.

As demonstrated by Caerbannog above and elsewhere in this site, McIntyre's criticisms of Mann have been poorly grounded, false or based on invalid statistics. Despite that, they have resulted in endless accusations of fraud, death threats, two congressional ordered inquiries and endless efforts to defame Mann of which yours is just the latest.

The 2001 hockey stick did not simply imply that the Current Warm Period is slightly warmer than the MWP scaddenp, it eliminated the MWP. That got it wrong. (-Snip-).

00

Response:

[DB] It has been pointed out to you a number of times now that both Mann and the science have moved on, that the "hockey stick" has been replicated in multiple reconstructions and in virtually every single temperature series and metric. Now it is time to move this dialogue on; you beat a dead horse.

dawsonjg @42, the following chart shows three reconstructions. The first in dark red is MBH 99, which was shown to underestimate centennial variability. The second from Esper et al 2002 (dark blue) used a method which is known to overestimate variability. Finally, the last is from Mann et al 2008 (Orange), and is typical of modern reconstructions:

As you can see, there is far more agreement between MBH 99 and the other two reconstructions during the MWP than there is during the LIA. So while there is some justification for saying MBH 99 eliminated the LIA, there is no justification for saying it eliminated the MWP.

For completeness, some modern reconstructions (including the Mann 2008 EIV method) show MWP temperatures 0.3 degrees C warmer than those shown by MBH 99 (and Mann et al 2008 CPS method). The fact that the use of two different but justifiable methods on the same data can result in that 0.3 C difference shows that reconstructions in that era are uncertain. But 0.3 C above MBH 99 (0.2 C above the mid 20th century baseline) is still 0.3 C less than modern temperatures.

Finally, I am unimpressed by deniers saying that in order to move on we just need to accept unjustified slanders against Michael Mann. The story about how they first came for the Jews comes to mind. If we allow unjustified slanders to stand against Mann, and cut him loose; deniers will just turn to their next target.

Nor are we defending any "sainthood" of Mann. MBH 98 and 99 had flaws, as has been shown by genuine scientific critiques, including by Mann himself. But I am not going to let lies about him stand just for the convenience of deniers who continue to make accusations without substantive evidence.

dawsonjg... One of the things people neglect to acknowledge about the 2001 MM graph is that it is just a 1000 year reconstruction. It does not eliminate the MWP but rather starts in the middle of the MWP. What disinformers have done is to focus on all the local temperature records that show the MWP warmer today, but ignoring the local records that show a MWP cooler than today, especially avoiding the records that show the records that are opposite sine from the MWP/LIA.

What I continually point out is the fact that the "skeptics" of the hockey stick have never managed to produce a multi-proxy reconstruction that shows anything other than a hockey stick.

Thanks Tom, since I must move on from Mann 1998, might I enquire about Mann 2008? Is it your conviction that during the intervening decade the wrinkles were ironed out and the new improved hockey stick got it pretty right?

00

Moderator Response: As I told you earlier, there is a more appropriate thread. Use it.

dawsonjg... It seems to me there are a plethora of reconstructions to choose from. No one study is going to be absolute but you can be pretty sure that if you have nearly a dozen projects returning very similar results that you've got a pretty robust conclusion.

Rob, I'm sure you meant Man Bradley and Hughes (MBH 99 rather than McIntyre and McKitrick (2001 MM). (I know your not confused, but I don't want casual readers to be confused by a mistype.) McIntyre and McKitrick's papers were in 2003 and 2005 (from memory).

First they came for the communists,
and I didn't speak out because I wasn't a communist.

Then they came for the trade unionists,
and I didn't speak out because I wasn't a trade unionist.

Then they came for the Jews,
and I didn't speak out because I wasn't a Jew.

Then they came for me
and there was no one left to speak out for me.

In his continued prosecution of his agenda, dawsonjg shows his disinterest in the science in favor of ideology. So we must needs continue to continually debunk these selfsame tired memes for what they truly are: empty and vacuous dissembling.

dawsonjg @25, this is venturing into of topic territory so any further discussion on this point should be taken to another thread.

For the record, it is possible to use the CO2 content of the atmosphere as a a measure of globally integrated sea surface temperature so long as net emissions are not large (ie, prior to the preindustiral era). Therefore based on the approximately 12 ppm difference in CO2 concentration between the peak of the MWP and the Maunder Minimum, there was approximately a 1 degree C difference in temperature between those times. On that basis, Moberg 2005 is likely to be a more accurate reconstruction than either Mann 2008 EIV or Mann 2008 CPS (where EIV and CPS refer to different reconstruction methods applied to the same data). However, as the following chart shows, the difference between the methods is small:

Based on that estimate, Moberg 2005 and Ljungqvist 2010 are both reasonably accurate. Mann 2008 EIV probably slightly overestimates MWP temperatures and LIA temperatures. Mann 2008 CPS is probably closer than the EIV result for the MWP but overestimates LIA temperatures. None of these estimates are certain enough to be considered the last word, however, all of them show MWP temperatures lower than 21st century (and late 20th century) temperatures. Given margins of error, it is possible but improbable that individual decades in the MWP were warmer than the the first decade of the 21st century. It is slightly more probable, but not very that some individual years in the MWP where warmer than the warmest years of the late 20th and early 21st century (1998, 2005, 2007, and 2010).